Method for fabricating a contact

ABSTRACT

A contact structure includes a permanent antireflection coating formed on a substrate having contact pads. A patterned dielectric layer is formed on the antireflective coating. The patterned dielectric layer and the permanent antireflective coating form openings. The openings correspond with locations of the contact pads. Contact structures are formed in the openings to make electrical contact with the contacts pads such that the patterned dielectric layer and the permanent antireflective coating each have a conductively filled region forming the contact structures.

RELATED APPLICATION INFORMATION

This application is a Divisional application of co-pending U.S. patentapplication Ser. No. 13/970,124 filed on Aug. 19, 2013, which is aDivisional application of co-pending U.S. patent application Ser. No.13/088,110 filed on Apr. 15, 2011, incorporated herein by reference intheir entirety. In addition, this application is related to commonlyassigned application Ser. No. 13/088,054 filed on Apr. 15, 2011, andcommonly assigned application Ser. No. 13/088,083 filed on Apr. 15,2011, both incorporated herein by reference.

BACKGROUND

1. Technical Field

The present invention relates to semiconductor contact structures andfabrication methods, and in particular to contact structures made bydirect patterning of dielectric material or by image reversalpatterning.

2. Description of the Related Art

Typical conventional integration schemes for forming electrical contactsfor transistors in a semiconductor chip include depositing a nitridestop layer on top of finished front end of line (FEOL) devices (e.g.,transistors). An oxide layer is deposited and planarized. Contactpatterns are formed by lithography on either a regular resist or resiston antireflection coating (ARC) mask stacks or multiple layer maskstacks, such as a tri-layer mask stack, which need to be removed inlater steps. Plasma etch processes are used to transfer the contactpatterns into the oxide layer by opening the ARC layer, etching throughthe oxide layer, which typically has a different thickness on the top ofgate and source/drain areas of the transistors, and then stopping on thenitride stopping layer. The nitride stopping layer is etchedthrough—stopping on silicide layers on tops of gate and source/drainareas.

Current integration schemes and process flows for contact formation etchcontact holes and stop on top of the gates and on the top of silicidesin the source/drain area. The etching is performed in five steps. Theseinclude open ARC, etch oxide (stop on the nitride stop layer), etch thenitride stop layer, strip the resist and ARC and perform a post plasmaetching treatment, e.g., Ar plasma sputtering step.

When device pitches shrink down to the sub-80 nm regime, there is nospace to accommodate a nitride stop layer between two gates withspacers. Without a nitride stop layer, it is extremely challenging foroxide etching processes to stop on the top of the gate or on the top ofsource/drain areas without damaging the silicide. Because of thenarrowing of pitch spaces between gates, self-aligned contact (SAC)integration schemes are being used to form contacts. The possibility ofmisalignment in the lithography steps can make the actual openings tothe source/drain areas very small, e.g., in the regime of less than 15nm. This shrinking of contact hole open area can cause severe aspectratio dependent etching (ARDE) or the so called reactive ion etch (RIE)lag effect. In a case of normal RIE lag, smaller open holes etch slowerthan those which have larger openings. In some instances, etching cantotally stop in very small holes, such as those having diameters lessthan 10 nm in diameter.

Because of the shrinking of silicide layer thicknesses, e.g., <10 nm for32 nm nodes and beyond, plasma etching of either the oxide layer or thenitride stopping layer can either thin or damage the silicide layer.Both effects can significantly increase the contact resistances ofsilicides on the tops of gates and source/drain areas. Because of theshrinking of contact hole openings, a pre-barrier layer deposition cleanprocess, usually a step of plasma etching with Ar sputtering, cansputter oxide from the oxide wall of the holes down to the bottoms ofholes to cause an increase in contact resistance.

SUMMARY

An electrically conductive contact structure includes a permanentantireflection coating formed on a substrate having contact pads. Apatterned dielectric layer is formed on the antireflective coating. Thepatterned dielectric layer and the permanent antireflective coating formopenings. The openings correspond with locations of the contact pads.Electrically conductive contact structures are formed in the openings tomake electrical contact with the contacts pads such that the patterneddielectric layer and the permanent antireflective coating each have aconductively filled region forming the contact structures.

A method for fabricating an electrically conductive contact includesforming a permanent antireflective coating on a substrate; forming aninterlevel dielectric composition on the antireflective coating whereinthe interlevel dielectric composition includes a material patternablewith irradiation and curable to become a permanent interlevel dielectriclayer; patterning the interlevel dielectric composition to form contactholes by exposing the interlevel dielectric composition to radiation anddeveloping the interlevel dielectric composition with a chemicalsolution; curing the interlevel dielectric composition therebyconverting the interlevel dielectric composition into a patternedpermanent interlevel dielectric layer; opening up the antireflectioncoating to expose contact pads within the contact holes; and filling thecontacts holes with an electrically conductive fill material to formelectrically conductive contacts.

Another method for fabricating a contact includes forming a permanentantireflective coating on a substrate; forming a pattern of resistislands in a first resist directly on the permanent antireflectivecoating, the resist islands occupying volumes where contacts will beformed; filling spaces between the resist islands with an interleveldielectric composition; removing the resist islands to form contactholes in the interlevel dielectric composition; opening up theantireflection coating to expose contact pads within the contacts holes;and filling the contacts holes with an electrically conductive fillmaterial to form contacts.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 shows a cross-sectional view of a device having a permanentantireflection coating and a patternable dielectric composition that canbe patterned like a resist and can be cured to form a permanentdielectric layer in accordance with one illustrative embodiment;

FIG. 2 shows a cross-sectional view of the device having the patternabledielectric composition of FIG. 1 patterned to form contacts holes aftera touch-up plasma etch to open the antireflection coating in accordancewith one illustrative embodiment;

FIG. 3 shows a cross-sectional view of the device showing thepatternable dielectric composition of FIG. 2 cured to form a permanentpatterned dielectric layer in accordance with one illustrativeembodiment;

FIG. 4 shows a cross-sectional view of the device showing the contactholes filled to form contacts in accordance with one illustrativeembodiment;

FIG. 5 shows a cross-sectional view of a device having a permanentantireflection coating and a resist layer in accordance with anotherillustrative embodiment;

FIG. 6 shows a cross-sectional view of the device of FIG. 5 having theresist layer patterned to form resist islands that create a reverseimage for contact holes in accordance with one illustrative embodiment;

FIG. 7 shows a cross-sectional view of the device of FIG. 6 having theresist islands buried in a patternable dielectric composition that canbe patterned like a resist and can be cured to form a permanentdielectric layer in accordance with one illustrative embodiment;

FIG. 8 shows a cross-sectional view of the device of FIG. 7 showing atop surface planarized to expose the resist islands in accordance withone illustrative embodiment;

FIG. 9 shows a cross-sectional view of the device having the patternabledielectric composition of FIG. 8 having contact holes after removing theresist islands in accordance with one illustrative embodiment;

FIG. 10 shows a cross-sectional view of the device of FIG. 9 having thepatternable dielectric composition being cured to form a permanentpatterned dielectric layer and the antireflection coating opened up toexpose contact pads in the contacts holes in accordance with oneillustrative embodiment; and

FIG. 11 shows a cross-sectional view of the device of FIG. 10 showingthe contact holes filled to form contacts in accordance with oneillustrative embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present principles provide electrically conductive contactstructures and methods for fabrication by direct patterning of thedielectric material or by an image reversal patterning technique. Inparticularly useful embodiments, new integration schemes are provided toform contacts. Nitride, oxide and resist mask stacks are replaced with apermanent antireflection coating and a patternable dielectriccomposition, which can be converted to a patterned and cured permanentdielectric layer. The patternable dielectric composition layer isdeveloped to transfer a pattern, i.e., via and/or bars. The dielectriccomposition layer is cured into a permanent dielectric structural layerto replace the oxide/nitride dielectric stack. It should be understoodthat the patternable dielectric composition may be formed as thepermanent dielectric layer upon deposition.

In some embodiments, drawbacks of conventional integration processes areavoided by, e.g., combining the functions of a photoresist and adielectric material into one material. This one material, which may bereferred to as a patternable low-k (low dielectric constant) materialherein, acts as a photoresist during the lithographic patterning processand, as such, a separate photoresist is not required or used herein.After lithographic patterning, the patternable low-k material issubsequently converted into a low-k material with a post patterningcure. In this way, the methods disclosed herein reduce plasma induceddielectric damage and the need for plasma etching, complex sacrificialfilm stacks and processes needed for patterning these stacks. Moreover,the methods disclosed herein also afford superior pattern profilecontrol.

The patternable low-k material permits the formation of customizablecontact hole shapes. The shapes are employed (as reverse images) to befilled by conductive material to form contacts or other structures. Thisflexibility permits the control of the conductor shape.

An antireflective coating (ARC) may be employed over front end of linestructures, such as transistors. An illustrative method for fabricating,e.g., a contact structure, in accordance with one illustrativeembodiment may include, depositing an anti-reflective layer on asubstrate, depositing a first positive- or negative-tone photoresist(preferably a patternable low-k material) and performing a pattern-wiseexposure to irradiation with an inversed-tone mask, e.g., ultraviolet(UV) light, extreme UV (EUV), E-beam, etc. Patterns (e.g., for contactholes) are formed by selective removal of the unexposed (or exposed)areas (e.g., development). Then, the patternable low-k material iscured. The contact holes are filled with a conductive fill material.

In some embodiments, an antireflective coating is formed on thesemiconductor substrate. In some embodiments, when an ARC is used, theARC and patternable low-k materials are part of a permanent dielectricmaterial stack of the interconnect structure.

In another embodiment which employs an image reversal integrationscheme, new integration schemes are provided to form electricallyconductive contacts. Nitride, oxide and resist mask stacks are replacedwith a permanent antireflection coating, a photoresist and a curabledielectric composition, which can be converted to a patterned and curedpermanent dielectric layer. The curable dielectric composition fills theopenings of the photo resist patterns which form contact holes and bars.The dielectric composition layer is cured into a permanent dielectricstructural layer to replace the oxide/nitride dielectric stack.

In accordance with the present principles, a number of photoresist stepsand all other sacrificial materials and their related deposition,pattern transfer (etch) and removal process used in prior artintegration are reduced. In addition, the need for plasma etching, whichis typically employed in patterning processes, is minimized. The reduceduse of plasma etching reduces plasma-induced contact damage, thusminimizing the increase in contact resistance of traditional integrationschemes. Further, the methods as described herein reduce a number oflayers needed to fabricate a contact structure and, as such, reduce thetime and cost of fabricating structures as compared to prior artprocesses.

In the following description, numerous specific details are set forth,such as particular structures, components, materials, dimensions,processing steps and techniques, to provide a thorough understanding ofthe present principles. However, it will be appreciated by one ofordinary skill in the art that these specific details are illustrativeand should not be construed as limiting.

It will be understood that when an element as a layer, region orsubstrate is referred to as being “on” or “over” another element, it canbe directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements may be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present.

As mentioned above, the interlayer dielectric materials employed hereinare preferably materials that act as a low-k (low dielectric constant)dielectric insulator after a cure process. The cured product of aninterlayer dielectric material, therefore, can serve as an on-chipdielectric insulator. The terms “cure” or “curing” are usedinterchangeable to refer to one of the processes selected from a thermalcure, an electron beam cure, an ultra-violet (UV) cure, an ion beamcure, a plasma cure, a microwave cure or a combination thereof. A“cured” product of an interlayer dielectric material is the product ofthe interlayer dielectric material after it has undergone a cureprocess. The “cured” product of an interlayer dielectric material may bedifferent from the original interlayer dielectric material in chemicalnature and physical, mechanical and electrical properties.

It is to be understood that the present invention will be described interms of a given illustrative architecture having a semiconductor waferor substrate; however, other architectures, structures, substratematerials and process features and steps may be varied within the scopeof the present invention.

Circuits or structures as described herein may be part of a design foran integrated circuit chip. The chip design may be created in agraphical computer programming language, and stored in a computerstorage medium (such as a disk, tape, physical hard drive, or virtualhard drive such as in a storage access network). If the designer doesnot fabricate chips or the photolithographic masks used to fabricatechips, the designer may transmit the resulting design by physical means(e.g., by providing a copy of the storage medium storing the design) orelectronically (e.g., through the Internet) to such entities, directlyor indirectly. The stored design is then converted into the appropriateformat (e.g., GDSII) for the fabrication of photolithographic masks,which typically include multiple copies of the chip design in questionthat are to be formed on a wafer. The photolithographic masks areutilized to define areas of the wafer (and/or the layers thereon) to beetched or otherwise processed.

The methods as described herein may be used in the fabrication ofintegrated circuit chips. The resulting integrated circuit chips can bedistributed by the fabricator in raw wafer form (that is, as a singlewafer that has multiple unpackaged chips), as a bare die, or in apackaged form. In the latter case the chip is mounted in a single chippackage (such as a plastic carrier, with leads that are affixed to amotherboard or other higher level carrier) or in a multichip package(such as a ceramic carrier that has either or both surfaceinterconnections or buried interconnections). In any case the chip isthen integrated with other chips, discrete circuit elements, and/orother signal processing devices as part of either (a) an intermediateproduct, such as a motherboard, or (b) an end product. The end productcan be any product that includes integrated circuit chips, ranging fromtoys and other low-end applications to advanced computer products havinga display, a keyboard or other input device, and a central processor.

The described embodiments demonstrate image reversal processes. An imagereversal is where positively formed (e.g., mask lines, resist lines orfeatures etc.) features will result in negative features being formed(e.g., vias and trenches) and vise versa. The negative features in thepresent embodiments will then be employed for forming interconnectstructures or the like. The interconnect structures are formed withoutetching interlevel dielectric layers to form trenches or vias. Instead,photoresists are employed to shape these trenches or vias and functionas an interlevel dielectric layer. In addition, the interleveldielectric material can be formed to provide a plurality of differentvertical profiles.

Referring now to the drawings in which like numerals represent the sameor similar elements and initially to FIG. 1, an illustrativecross-sectional view of front end of line (FEOL) structures is depicted.The structures include a metal oxide semiconductor field effecttransistor (MOSFET) 100, which includes a complementary MOS (CMOS)device having an n-FET 102 and a p-FET 104. The n-FET 102 and p-FET 104are formed in a semiconductor substrate 108. The substrate 108 and then-FET 102 and p-FET 104 have an antireflection coating (ARC) 110 formedthereon.

The substrate 108 may include a semiconductor substrate, e.g., silicon,GaAS, silicon on insulator, etc. Although the substrate 108 shown is fora FEOL structure, the present principles are applicable to formingcontacts on other layers of a semiconductor device structure. As such,the substrate 108 may include an electrically semiconducting material,an insulating material, a conductive material, devices or structuresmade of these materials or any combination thereof (e.g., a lower levelof an interconnect structure). When the substrate 108 is comprised of asemiconducting material, any semiconductor such as Si, SiGe, SiGeC, SiC,Ge alloys, GaAs, InAs, InP and other III/V or II/VI compoundsemiconductors, or organic semiconductors may be employed. The substrate108 may also be a flexible substrate including devices that are suitablefor high-speed roll-to-roll processing. In addition to these listedtypes of semiconducting materials, substrate 108 may also be a layeredsemiconductor such as, for example, Si/SiGe, Si/SiC,silicon-on-insulators (SOIs) or silicon germanium-on-insulators (SGOIs).These semiconductor materials may form a device, or devices (n-FET 102and p-FET 104) or structures, which may be discrete or interconnected.These devices and device structures may be for computation,transmission, storage or display of information, such as logic devices,memory devices, switches or display devices.

When the substrate 108 is an electrical insulating material, theinsulating material can be an organic insulator, an inorganic insulatoror a combination thereof including multilayers. The substrate 108 mayalso include a patternable low-k dielectric material as well. Theseelectrical insulating materials may be part of a device, or devices orstructures, which may be discrete or interconnected. These devices andstructures may be for logic applications or memory applications. Whenthe substrate 108 is an electrically conducting material, the substratemay include, for example, polysilicon, an elemental metal, an alloyincluding at least one elemental metal, a metal silicide, a metalnitride or combinations thereof including multilayers. When thesubstrate 108 includes a semiconducting material, one or moresemiconductor devices such as, for example, complementary metal oxidesemiconductor (CMOS) devices, strained silicon devices, carbon-based(carbon nanotubes and/or graphene) devices, phase-change memory devices,magnetic memory devices, magnetic spin switching devices, singleelectron transistors, quantum devices, molecule-based switches and otherswitching or memory devices that can be part of an integrated circuit,can be fabricated thereon.

Substrate 108 may include shallow trench isolation structures 112 toprevent charge leakage between devices. The n-FET device 102 includessource and drain regions 114 and 116, which have silicided regions 118formed thereon. The p-FET device 104 also includes source and drainregions 120 and 122, which have silicided regions 124 formed thereon.The n-FET device 102 and p-FET 104 include gate structures 126. Theseinclude a gate dielectric 128 with a gate conductor 130 (e.g., dopedpolysilicon, or a metal gate for high dielectric constant gatedielectrics). In one embodiment, the gate structures 126 include dopedmonocrystalline silicon regions 132 with silicided regions 134. Thesilicided regions 118, 124 and 134 provide landing sites for laterformed contacts. The gate structures 128 also include low temperatureoxide (LTO) offset spacers 136 and spacers 138 (e.g., nitride).

It should be understood that the device structures shown areillustrative and that other structures, such as FinFETs and devicetypes, such as carbon based transistors and organic transistors, arecontemplated and may be employed in accordance with the presentprinciples.

The ARC 110 is formed on a surface of the devices 102, 104 and substrate108 and, in particular over silicided regions 118, 124 and 134. Thesilicided regions 118, 124 and 134 form contact pads. The ARC 110 may bea single layer, multilayer or a graded layer with a composition thatvaries along the vertical direction. The ARC 110: (i) acts as anantireflective coating (ARC) during a lithographic patterning process;(ii) withstands high-temperature processing (e.g., up to about 1000°C.); (iii) prevents patterning film (e.g., resist or a patternable low-kmaterial) poisoning by the substrate 108; (iv) provides sufficient etchselectivity between the patternable low-k material and the ARC layer110; (v) serves as a permanent dielectric layer in a chip (lowdielectric constant, e.g., k<15, more commonly k<7.0); and (vi) iscompatible with conventional integration and produces reliable hardware.

Antireflective coatings (ARC) 110 are known to those skilled in the artand include, for example, organic homopolymers or copolymers ofpolyesters, polyimides, polyacrylates, polymethacrylates, polysulfones,and amorphous carbon that satisfy all of the characteristics of ARC 110mentioned above. The ARC 110 may be applied by spin-on techniques, sprayon techniques, dipping, etc. Inorganic antireflective coatings, such assilicon oxynitride (SiON), silicon carbide (SiC), silicon oxycarbide(SiOC), SiCOH, siloxane, silane, carbosilane, oxycarbosilane, andsilsesquioxane, either as a polymer or a copolymer may also be employedand may be deposited, for example, by plasma-enhanced chemical vapordeposition, atomic layer deposition, spin-on techniques, dipping, etc.The ARC 110 may include atoms of M, carbon (C) and hydrogen (H), whereinM is at least one of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La. Thethickness of the ARC 110 may vary depending on the technique used toform the same as well as the material make-up of the layer. The ARC 110may have a thickness from about 1 to about 200 nm, with a thickness fromabout 10 to about 100 nm being more common.

When ARC 110 is a multilayer ARC, the deposition of each layer may bethe same or a combination of deposition methods can be used. Afterapplying ARC 110, particularly from a liquid phase, a post depositionbaking step is usually needed to remove unwanted components, such assolvent, and to effect crosslinking. The post deposition baking step ofARC 110 may be performed at a temperature from 80° C. to 300° C., with abaking temperature from 120° C. to 200° C. being even more likely. Otherpost-deposition treatments may be performed.

A resist material, patterning film or patternable low-k material 140 isdeposited on the ARC 110. The material 140 may include chemicallyamplified photoresists, non-chemically amplified photoresists,positive-tone or negative tone. Processing of material 140 may include adeposition process including, for example, spin-on-coating, dip coating,brush coating, and ink-jet dispensing. After applying the material 140,a post deposition baking step may be performed to remove unwantedcomponents, such as solvent. When performed, the baking step isconducted at a temperature from 40° C. to 200° C., with a bakingtemperature from 60° C. to 140° C. being even more preferred. Theduration of the baking step varies from 10 seconds to 600 seconds and isnot critical.

The thickness of the material 140 may vary depending on the requirementsof a chip being fabricated, the method being employed to form the same,and the make-up of the material 140. The patternable low-k material 140may have a thickness from 1 nm to 50,000 nm, with a thickness from 10 nmto 500 nm being preferred. The pattern-wise exposing process can beaccomplished in a variety of ways, including, for example, exposurethrough a mask with a lithography stepper or a scanner with an exposurelight source of G-line, Mine (365 nm), DUV (248 nm, 193 nm, 157 nm, 126nm), Extreme UV (13.4 nm, 6.5 nm), an electron beam, an ion beam, etc.The exposing process may be performed in a dry mode or an immersionmode. The exposing process may be performed with a single exposure ormultiple exposures. The pattern-wise exposing process may include directwriting without the use of a mask with, for example, light, electronbeam, ion beam, and scanning probe lithography. Other patterningtechniques that can be used include contact printing techniques such asnanoimprint lithography, embossing, micro contact printing, replicamolding, microtransfer molding, micromolding in capillaries andsolvent-assisted micromolding, thermal assisted embossing, injectprinting, and the like.

An optional post-exposure baking may be employed to effect thephotochemical reactions. When performed, the baking step is conducted ata temperature from 60° to 200° C., with a baking temperature from 80° to140° C. being even more typical. The duration of the baking step variesand is not critical to the practice of the present invention. When thedielectric layer is permanent it preferably has a dielectric constant ofno more than 10, more preferably no more than 4.3. The permanentantireflective coating layer has a dielectric constant of no more than15, and preferably no more than 7.0.

Referring to FIG. 2, a positive- or negative-tone patternable low-kmaterial 140 is employed to form contact holes 144. The mask is alignedwith the silicide regions 118, 124 and 134. The layer 140 is exposed toirradiation and then developed. The holes 144 provide channels to formelectrical contacts later. Since the holes 144 are patterned usinglithographic methods, the pattern features 144 may be formed with aplurality of different shapes and sizes, as illustratively depicted.

After exposure and post-exposure baking, latent images or patterns aredeveloped into relief images or patterns to form the holes 144 with anappropriate developer, usually an aqueous base solution, such as a 0.26Ntetramethylammoniahydroxide (TMAH) solution. A touch-up plasma etch orequivalent process is performed to open up the ARC 110 and expose thesilicided regions 118, 124, 134 in the bottom of holes 144.

Referring to FIG. 3, in one preferred embodiment, the patterning film140 preferably includes a photo-patternable low k (PPLK) material. It isnoted that the photo-patternable low k (PPLK) materials employed hereinmay include any dielectric materials possessing two functions. They actas a photoresist during a patterning process and are subsequentlyconverted into a low-k dielectric insulator during a post patterningcure process. The cured product of a PPLK material, therefore, can serveas a permanent on-chip dielectric insulator. The photo-patternable low kmaterial employed herein can be deposited from a liquid phase. In thepresent disclosure, the terms “cure” or “curing” are usedinterchangeable to refer one of the processes selected from a thermalcure, an electron beam cure, an ultra-violet (UV) cure, an ion beamcure, a plasma cure, a microwave cure or a combination thereof.

A “cured” product of a photo-patternable low k material is the productof the photo-patternable low k material after it has undergone one ofthe aforementioned cure processes. The “cured” product of aphoto-patternable low k material is different from the photo-patternablelow k material in chemical nature and physical, mechanical andelectrical properties.

The term “photo-patternable low k material” (or PPLK) includes afunctionalized polymer, copolymer or blend including at least two of anycombination of polymers and/or copolymers having one or moreacid-sensitive imageable groups. The PPLK material acts as a photoresistand after curing it is converted into a dielectric material having adielectric constant of about 7.0 or less. It is noted that when the PPLKmaterial is comprised of a polymer, the polymer includes at least onemonomer (to be described in greater detail below). When the PPLKmaterial is comprised of a copolymer, the copolymer includes at leasttwo monomers (to be described in greater detail below). The blends ofpolymers and/or copolymers include at least two of any combination ofpolymers and/or copolymers described herein.

The PPLK material is a photo-patternable composition including apolymer, a copolymer, or a blend including at least two of anycombination of polymers and/or copolymers, wherein the polymers includeone monomer and the copolymers include at least two monomers and whereinthe monomers of the polymers and the monomers of the copolymers areselected from a siloxane, silane, carbosilane, oxycarbosilane,silsesquioxane, alkyltrialkoxysilane, tetra-alkoxysilane, unsaturatedalkyl substituted silsesquioxane, unsaturated alkyl substitutedsiloxane, unsaturated alkyl substituted silane, an unsaturated alkylsubstituted carbosilane, unsaturated alkyl substituted oxycarbosilane,carbosilane substituted silsesquioxane, carbosilane substitutedsiloxane, carbosilane substituted silane, carbosilane substitutedcarbosilane, carbosilane substituted oxycarbosilane, oxycarbosilanesubstituted silsesquioxane, oxycarbosilane substituted siloxane,oxycarbosilane substituted silane, oxycarbosilane substitutedcarbosilane, and oxycarbosilane substituted oxycarbosilane.

More specifically, the PPLK material that can be employed is aphoto-patternable composition comprising a photo/acid-sensitive polymerof one monomer or a copolymer of at least two monomers selected fromsiloxane, silane, carbosilane, oxycarbosilane, organosilicates,silsesquioxanes and the like. The PPLK material may also bephoto-patternable composition comprising a polymer of one monomer or acopolymer of at least two monomers selected from alkyltrialkoxysilane,tetra-alkoxysilane, unsaturated alkyl (such as vinyl) substitutedsilsesquioxane, unsaturated alkyl substituted siloxane, unsaturatedalkyl substituted silane, an unsaturated alkyl substituted carbosilane,unsaturated alkyl substituted oxycarbosilane, carbosilane substitutedsilsesquioxane, carbosilane substituted siloxane, carbosilanesubstituted silane, carbosilane substituted carbosilane, carbosilanesubstituted oxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane.

Additionally, the PPLK material may comprise a blend including at leasttwo of any combination of polymers and/or copolymers, wherein thepolymers include one monomer and the copolymers include at least twomonomers and wherein the monomers of the polymers and the monomers ofthe copolymers are selected from a siloxane, silane, carbosilane,oxycarbosilane, silsesquioxane, alkyltrialkoxysilane,tetra-alkoxysilane, unsaturated alkyl substituted silsesquioxane,unsaturated alkyl substituted siloxane, unsaturated alkyl substitutedsilane, an unsaturated alkyl substituted carbosilane, unsaturated alkylsubstituted oxycarbosilane, carbosilane substituted silsesquioxane,carbosilane substituted siloxane, carbosilane substituted silane,carbosilane substituted carbosilane, carbosilane substitutedoxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane.

Optionally, the PPLK material may be a photo-patternable compositionfurther comprising at least one microscopic pore generator (porogen).The pore generator may be or may not be photo/acid sensitive.

Illustrative polymers for the PPLK material include, but are not limitedto, siloxane, silane, carbosilane, oxycarbosilane, silsesquioxane-typepolymers including caged, linear, branched or combinations thereof. Inone embodiment, the PPLK material is a photo-patternable compositioncomprising a blend of these photo/acid-sensitive polymers.

The PPLK material is formed from a photo-patternable composition(negative-tone or positive-tone) that includes at least one of the abovementioned polymers, copolymers or blends, a photoacid generator, a baseadditive and a solvent used in a photoresist composition. When the PPLKmaterial is a negative-tone photo-patternable material, it may be formedfrom a patternable composition optionally including an additionalcross-linker. By “negative-tone” it is meant that the part of the PPLKmaterial that is exposed to an actinic irradiation will not be removedby a conventional developer, while the unexposed part of the PPLKmaterial is removed.

The additional cross-linker can be a small compound (as compared with apolymer or copolymer) or a polymer, a copolymer, or a blend including atleast two of any combination of polymers and/or copolymers, wherein thepolymers include one monomer and the copolymers include at least twomonomers and wherein the monomers of the polymers and the monomers ofthe copolymers are selected from a siloxane, silane, carbosilane,oxycarbosilane, silsesquioxane, alkyltrialkoxysilane,tetra-alkoxysilane, unsaturated alkyl substituted silsesquioxane,unsaturated alkyl substituted siloxane, unsaturated alkyl substitutedsilane, an unsaturated alkyl substituted carbosilane, unsaturated alkylsubstituted oxycarbosilane, carbosilane substituted silsesquioxane,carbosilane substituted siloxane, carbosilane substituted silane,carbosilane substituted carbosilane, carbosilane substitutedoxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane.

When the PPLK material is a positive-tone photo-patternable material, itis formed from a patternable composition that includes at least one ofthe above mentioned polymers, copolymers or blends wherein the polymers,copolymers or blends containing at least photo/acid imageable functionalgroup to form positive-tone patterns, a photoacid generator, a baseadditive and a solvent used in a photoresist. By ‘positive-tone” it ismeant that the part of the PPLK material that is exposed to an actinicirradiation will be removed by a conventional developer, while theunexposed part of the PPLK material is not removed. The photoacidgenerators, base additives and solvents are well known to those skilledin the art.

The patterning film 140 is cured. The curing may be performed with heat,UV, or E-beam. The cured patterning film 140 (with e.g., PPLK material)provides a permanent dielectric material 150 which is employed toinsulate conductive structures. Curing is performed by a thermal cure,an electron beam cure, an ultra-violet (UV) cure, an ion beam cure, aplasma cure, a microwave cure or a combination thereof. The conditionsfor each of the curing processes are known to those skilled in the artand any condition can be chosen as long as it coverts thephoto-patternable low k material into a low k film and maintains patternfidelity.

In one embodiment, an irradiation cure step is performed by acombination of a thermal cure and an ultra-violet (UV) cure wherein thewavelength of the ultra-violet (UV) light is from 50 nm to 300 nm andthe light source for the ultra-violet (UV) cure is a UV lamp, an excimer(exciplex) laser or a combination thereof. The excimer laser may begenerated from at least one of the excimers selected from the groupconsisting of Ar₂*, Kr₂*, F₂, Xe₂*, ArF, KrF, XeBr, XeCl, XeCl, XeF,CaF₂, KrCl, and Cl₂ wherein the wavelength of the excimer laser is inthe range from 50 nm to 300 nm. Additionally, the light of theultra-violet (UV) cure may be enhanced and/or diffused with a lens orother optical diffusing device known to those skilled in the art.

In one embodiment, this post patterning cure is a combined UV/thermalcure. This combined UV/thermal cure is carried on a UV/thermal curemodule under vacuum or inert atmosphere, such as, in N₂, He or Ar. TheUV/thermal cure temperature may be from 100° C. to 500° C., with a curetemperature from 300° C. to 450° C. being more common. The duration ofthe UV/thermal cure is from 0.5 min to 30 min with duration from 1 minto 10 min being more common. The UV cure module is designed to have avery low oxygen content to avoid degradation of the resultant dielectricmaterials. This post-patterning cure, if performed, may be in differentor the same tool cluster as that of the patterning step.

The thickness of the patterned and cured PPLK material 150 may varydepending on the requirements of the chip and the technique used to formthe same, as well as the material make-up of the layer. The first PPLKmaterial 150 may have a thickness, e.g., from 1 nm to 50000 nm, with athickness from 10 nm to 500 nm being preferable.

Referring to FIG. 4, a metallization process includes depositing aconductor 152 into holes 144 in layer 150 and over a top surface oflayer 150. The conductor 152 may include copper, aluminum, tungsten,titanium, tantalum, electrically conductive carbon materials such ascarbon nanotubes and graphene, doped polysilicon or any other usefulconductive materials, or alloys/combinations thereof. The conductivecontact structure as may include a barrier layer when the conductivecontact metal is Cu or a conductive catalyst when the conductive carbonmaterials are employed.

The conductor 152 may be deposited using chemical vapor deposition(CVD), atomic layer deposition, plating, or other deposition techniquesor directly grown from the source, drain regions and the gate contactregions. The holes 144 are filled with electrically conductive material152 which takes the shape of the holes 144.

A chemical-mechanical polish (CMP) is performed to remove excessconductor 152 from the surface of dielectric layer 150 to form contacts154 in contact with contact pads (e.g., silicides regions 118, 124 and134) in accordance with the present principles. Other planarizationprocesses may also be employed. It should be understood that the layer150 is shaped using irradiation and includes a high degree of accuracywithout etching open the contact holes 144. Contacts 154 formed withincontact holes 144 therefore are more accurately shaped which results inimproved reliability. In addition, all contact sizes and shapes withlayer 150 are processed simultaneously, which eliminates a plurality ofdeposition, masking and etching steps—making the process more efficientand less expensive. For example, process steps in the conventionalintegration schemes, such as, nitride deposition, oxide deposition,oxide CMP, multiple plasma etching steps, including, ARC open, oxideetching, nitride etching, resist stripping, etc. are eliminated. Inparticular, a nitride stopping layer is eliminated, which has a higherdielectric constant, e.g., k˜7.4, compared with a k value of, e.g.,about 4.5 of in a PPLK ARC layer (110). This k value reduction canreduce parasitic capacitance between gates and contact metal studsand/or bars, which can result in the improvement of device performance.

Plasma etching steps are eliminated in accordance with the presentprinciples. Plasma etching steps are the most challenging process stepsin the contact formation especially in attempting to make conventionalself-aligned contact (SAC) integration achievable when gate pitchshrinks down to, e.g., less than 50 nm or so. Eliminating plasma etchingsteps in accordance with the present principles reduces damage ofsilicide layers and further improves the contact resistance.

In the present example, the contacts 152 have less width at a lowerportion and a greater width at a top portion. The contacts 152 mayinclude other graduated shapes or stepped shapes as well. It should beunderstood that the silicided regions 118, 124 and 134 represent onetype of contact pad. Other types of contact pads may also be employed.Processing can continue using the inventive processes or conventionalprocesses.

Referring to FIG. 5, in another embodiment, resist image reversal isemployed to form contact holes in accordance with the presentprinciples. ARC layer 110 and a resist layer 202 are formed as describedwith reference to FIG. 1. Resist layer 202 may employ a reversed-tonemask and a positive- or negative-tone photoresist to form inversepatterns for contact hole formation.

Referring to FIG. 6, using a lithographic mask (not shown), resist layer202 is exposed (or prevented from being exposed) to (from) irradiationto form cross-linked pillars or resist island structures 204. Theremaining portions of resist layer 202 are removed by a developer toprovide the structure shown. The pattern-wise exposure to irradiationmay include, e.g., UV light, e-beam, EUV with an inversed-tone mask.

Referring to FIG. 7, a dielectric composition 206 is deposited. Thedeposition process includes, for example, spin-on-coating, dip coating,brush coating, doctor blade coating, and ink-jet dispensing. Thedielectric composition 206 is formulated such that it is compatible withthe underlying photoresist pattern 204, i.e., the application of thedielectric composition 206 does not substantially alter the dimensionand profile of the resist patterns 204. After applying the dielectriccomposition 206, a post deposition baking step may be employed to removeunwanted components, such as solvent. When performed, the baking step isconducted at a temperature from 40° C. to 200° C., with a bakingtemperature from 60° C. to 140° C. being even more preferred. Theduration of the baking step varies from 10 seconds to 600 seconds and isnot critical.

In one embodiment, the dielectric composition 206 may include a PPLKmaterial, which can be converted into a patterned and cured permanentdielectric layer in later steps. Layer 206 may be applied using aspin-on process or a chemical vapor deposition (CVD) process. Thecomposite layer is formed by filling resist openings wherein the fillingshould not distort the resist patterns/islands 204. The dielectriccomposition 206 may include other dielectric materials as well.

Referring to FIG. 8, the dielectric layer 206 is planarized using, e.g.,a dry or wet etch to expose a top surface 205 of the resist islandstructures 204.

Referring to FIG. 9, the resist of the island structures 204 is removedfrom the resist layer 206 to leave contact holes 212 with ARC 110remaining at the bottom of the holes 212. This exposes resist islandstructures 204, which may be removed by a wet method, a dry method,heat, UV light or a combination thereof. In one embodiment, a wet methodis employed with an appropriate developer after exposing the dielectricand resist composite structure to a blanket UV irradiation. In anotherembodiment, a dry method is employed with an appropriate selectivereactive ion etching that removes only the exposed resist. In yetanother embodiment, a dry method is employed by using heat or UVirradiation to remove exposed resist islands.

Referring to FIG. 10, the layer 206 may be cured as described above toconvert the resist layer 206 into a patterned and cured permanentdielectric layer 210. This step is not needed in the layer 206 is formedas a permanent dielectric material (210). The pattern in layer 210corresponds to contact holes 212 that will be employed to form contactsin later steps. An ARC open process is performed to open the ARC 110 forsource, drain and gates contacts. The ARC open process is as describedabove and exposes the silicided regions 118, 124 and 134 in contactholes 212.

Referring to FIG. 11, a conductive material 214 is deposited to fill thecontact holes 212 and is formed over a surface of the dielectric layer210. A CMP process may be performed to planarize the top surface. Theconductive material may include, copper, aluminum, tungsten, titanium,tantalum, ruthenium their alloys electrically conductive carbonmaterials such as carbon nanotubes and graphene, doped polysilicon orany other useful conductive material, or alloys/combinations thereof.

This integration scheme forms contacts 220 using a photoresist imagereversal method to replace the nitride, oxide, and the resist mask stackof conventional process with a permanent resist base dielectric layerand permanent ARC. The present method reduces many process steps ofconventional integration schemes, such as, e.g., nitride deposition,oxide deposition, oxide CMP, multiple plasma etching steps, including,oxide etching, nitride etching, resist stripping, etc. Plasma etchingsteps are also eliminated.

Having described preferred embodiments for middle of line structures andmethods for fabrication (which are intended to be illustrative and notlimiting), it is noted that modifications and variations can be made bypersons skilled in the art in light of the above teachings. It istherefore to be understood that changes may be made in the particularembodiments disclosed which are within the scope of the invention asoutlined by the appended claims. Having thus described aspects of theinvention, with the details and particularity required by the patentlaws, what is claimed and desired protected by Letters Patent is setforth in the appended claims.

What is claimed is:
 1. A method for fabricating a contact, comprising:forming a permanent antireflective coating on a substrate with contactpads therebetween; forming a pattern of resist islands in a first resistdirectly on the permanent antireflective coating, the resist islandsoccupying volumes where contacts will be formed; filling spaces betweenthe resist islands with an interlevel dielectric composition; removingthe resist islands to form contact holes in the interlevel dielectriccomposition; opening up the antireflection coating to expose the contactpads within the contacts holes; and filling the contacts holes with anelectrically conductive fill material to form contacts.
 2. The method asrecited in claim 1, wherein the substrate includes front end of linedevices and forming a permanent antireflective coating on a substrateincludes forming the antireflection coating over the front end of linedevices.
 3. The method as recited in claim 1, wherein the interleveldielectric composition includes at least one of a polymer, a copolymer,a blend including at least two of any combination of polymers and/orcopolymers, wherein the polymers include one monomer and the copolymersinclude at least two monomers and wherein the monomers of the polymersand the monomers of the copolymers are selected from: a siloxane,silane, carbosilane, oxycarbosilane, silsesquioxane,alkyltrialkoxysilane, tetra-alkoxysilane, unsaturated alkyl substitutedsilsesquioxane, unsaturated alkyl substituted siloxane, unsaturatedalkyl substituted silane, an unsaturated alkyl substituted carbosilane,unsaturated alkyl substituted oxycarbosilane, carbosilane substitutedsilsesquioxane, carbosilane substituted siloxane, carbosilanesubstituted silane, carbosilane substituted carbosilane, carbosilanesubstituted oxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane.
 4. The method as recited in claim 1, wherein theinterlevel dielectric composition includes a material curable to becomea permanent interlevel dielectric layer, the method further comprisingcuring the interlevel dielectric composition thereby converting theinterlevel dielectric composition into a patterned permanent interleveldielectric layer.
 5. The method as recited in claim 1, wherein thecontact pads include silicided regions.
 6. The method as recited inclaim 1, wherein the conductive fill material includes at least one ofCu, W, Ta, Ti, Ru, their alloys and conductive carbon materials.
 7. Themethod as recited in claim 1, wherein patterning the interleveldielectric composition includes forming contact holes having differentdimensions in a same patterning process.
 8. The method as recited inclaim 1, wherein the interlevel dielectric composition is formed by oneof a spin-on and a chemical vapor deposition process.